The American University in CairoMechanical Engineering DepartmentMENG 426: Metals, Alloys & Composites Interactive MENG 426 Lab Tutorials Experiment (6) Cast Iron Prepared by Eng. Moataz M. Attallah Fall 2002
Outline • Introduction: steel and cast iron • Cast iron properties • Cast iron types • Specimens • Lab report
CARBON STEELS STAINLESS STEELS ALLOY STEELS Low carbon (Mild) steel 0.3% C Medium carbon 0.3-0.6% C High-carbon >0.6% C Steel Alloys Austenitic Ferritic Martensitic Ppt. Hard. High strength low-alloy HSLA
Cast Iron • Carbon content ranging from 2-4.3% • Castable, hard & strong • Wide range of types depending on: • The chemical composition of the iron; the existence of certain alloying elements. • The cooling rate of the casting in the mould. • The type of graphite formed and its percent composition.
Cast Iron Types • Gray (graphite flakes) CI • Malleable CI • Nodular (ductile/spherulitic) CI • White CI
Pearlitic matrix Graphite flakes Gray (Graphite Flakes) CI • Gray fracture surface • Maximum C% • C precipitate as flakes • High Si% forms flakes • Good wear resistance, vibration damping machineability
Spherulites Pearlitic matrix Ductile (Nodular/spherulitic) CI • C precipitates in black nodules • High fluidity/castability Good machineability Wear resistance • Alloy elements produce nodules
Nodular Cast Iron • Desulfurization • Nodules formation • Inoculation
Cementite Pearlitic matrix White CI • Iron carbide forms instead of iron and graphite • Iron carbide in pearlite • White fracture surface
Pearlitic matrix Graphite clump Malleable CI • Initially formed as white CI • Heat-treated in malleablizing furnace to dissociate Fe3C to iron and graphite • Good wear resistance Ductility Fluidity
Objectives • Focus on the cast iron zone in the iron-iron carbide system. • Get acquainted with the different types of cast irons, and the differences between them in microstructure, mechanical & physical properties. • Study the different microstructures of the different types of cast iron.
Specimens • Gray cast iron • Nodular cast iron • Malleable cast iron • Common grinding and polishing • Etching using 3ml of HNO3 + 100 ml of CH3OH (methyl alcohol), etched by immersing for 15 seconds.
Results • Sketch and describe the microstructure